Control Systems Introduction PDF

 Analysis is the process by which a system’s performance is determined.  For example: evaluate transient response and steady-state error to determine if they meet the desired specs.  - is the process by which a system’s performance is created or changed. Example: If transient response...

 Analysis is the process by which a system’s performance is determined.  For example: evaluate transient response and steady-state error to determine if they meet the desired specs.  - is the process by which a system’s performance is created or changed. Example: If transient response and steady-state error are analyzed & found not to meet the specifications, then we change parameters or add additional components to meet the specifications.  In a computer, transient response contributes to the time required to read or write to the computer’s disk storage.  This response resembles the input and is usually what remains after the the transient have decayed to zero.  We are concerned about the accuracy of the steady-state response  Example: - elevator must be level enough to with the floor for the passengers to exit.  -- an antenna tracking a satellite must keep the satellite within its beamwidth in order not to lose track. -- disk drive finally stopped at the right track  Control sytems must be designed to be stable That is, their natural response must decay to zero as time approaches infinity, or oscillate. -- instability could lead to self destruction of the physical device if limit stops are not part of the design.  hardware selection  Finances  Robust design  --- the system will not be sensitive to parameter changes.  STEP 1: transform requirements into physical systems. example: the antenna azimuth position control system, the requirements would state the desire to position the antenna from a remote location & describe such features as weight & physical dimensions. Using the requirements, design specs, such as desired transient response and steady state accuracy, are determined.  Draw a functional block diagram -- translate a qualitative description of the system into functional block diagram that describes the components parts of the system( fucntion and/or hardware ) & show their interconnection.  CREATE SCHEMATIC - after producing the description of a physical system, the control system engineer transforms the physical systems into schematic diagram. -the engineer must make approximations about the system & neglect certain phenomena, or else the schematic will be unwieldy. - the designer starts with a simple schematic representation  STEP 4: Develop a Mathematical Model ( block diagram)  Use KCL, KVL, Newton’s Law, Differential Equation, Laplace transform, transfer function, state-space representation  To produce mathematical model for a system, we require knowledge of the parameter values, such as equivalent resistance, mass, and damping, w/c is not easy to obtain. Analysis, measurements, or specs from vendors are sources that the control system engineer may use to obtain the parameters.  Step 5: Reduce the Block Diagram  --- reduce the large system’s block diagram to a single block diagram with mathematical description that represents the system from input to its output.  ----once the block diagram is reduced, we are ready to analyze the and design the system.  Step 6: Analyze and design  See if the response specs and performance requirements can be met by simple adjustments of system parameters.  If not, design additional hardware to effect a desired performance.  use test inputs like unit impulse, unit step, ramp etc.